When secondary is important

Technicians and engineers have just tested a key part of the telescope unfolding mechanism for the James Webb Space Telescope by commanding JWST to deploy the support structure that holds its secondary mirror in place. 

Far from secondary, this mirror – visible in the top right corner of this image – is actually among the most important parts. Folded together with the other observatory components during launch, it will be deployed as part of an intricate choreography that will bring the observatory to life once in space. 

When deployed, it faces JWST’s honeycomb-like pattern of 18 hexagonal, gold-coated primary mirror segments. This primary mirror structure is seen in the lower left of the image in its folded configuration, showing only 12 segments.

The JWST is an international project led by NASA with its partners, ESA and the Canadian Space Agency. It is scheduled for launch on a European Ariane 5 rocket from French Guiana in March 2021.

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